1. Field of the Invention
The present invention relates to a tank system including multiple tanks and a control method of regulating release flow rates from the multiple tanks in the tank system.
2. Description of the Related Art
There is conventionally a tank system including multiple tanks for storing high-pressure gases. For example, in a fuel cell system that generates and outputs electric power through electrochemical reactions of hydrogen and oxygen, multiple high-pressure tanks are connected in series for storage of a large quantity of hydrogen gas. In the fuel cell system, the inherent structure of fuel cells requires reduction of the hydrogen gas flowing on the circuit to the low pressure. In a prior art structure, a pressure reducing valve is set in the vicinity of the mouth of each high-pressure tank to significantly reduce the pressure of the hydrogen gas, and the hydrogen gas of the reduced pressure is supplied to a downstream device located downstream of the high-pressure tanks (see, for example, Japanese Patent Laid-Open Gazette No. 2002-370550).
The fuel cell system of this arrangement requires high-pressure piping between the high-pressure tanks and the pressure reducing valves. The shortest possible high-pressure piping is desired on safety grounds. In one proposed structure, a pressure reducing valve is directly set at the mouth of each high-pressure tank to reduce the pressure of the hydrogen gas released from the mouth of the tank.
In this prior art system including multiple high-pressure tanks with pressure reducing valves, however, it is difficult to individually regulate the release flow rates of the hydrogen gas from the respective high-pressure tanks. This is ascribed to a little variation in setting of the secondary pressure among the pressure reducing valves located at the respective high-pressure tanks. The hydrogen gas is preferentially released from a high-pressure tank having a higher setting of the pressure reducing valve, among the multiple high-pressure tanks. The preferential release of the gas from only a particular tank having the higher setting of the pressure reducing valve causes uneven release rates (consumptions) and leads to an abrupt temperature change, which is disadvantageous for the strength of the tank structure.